Means for preparing gas-treated objects



Jan. 17, 1967 P. s. STOKES MEANS FOR PREPARING GAS-TREATED OBJECTS 2 Sheets-Sheet 1 Filed June 4, 1964 FIG.

INVENTOR PETER GRANVILLE STOKES BY 2 2M w J /9A- ATTORNEYS Jan. 17, 1967 P. G. STOKES 3,298,112

MEANS FOR PREPARING GASTREATED OBJECTS Filed June 4, 1964 2 Sheets-Sheet 2 INVENTOR PETER GRANVILLE STOKES ATTORNEYS United States Patent MEANS FOR PREPARING GAS-TREATED OBJECTS Peter Granville Stokes, Slough, England, assignor to Westlaud Aircraft Limited, Somerset, England Filed June 4, 1964, Ser. No. 372,627 Claims priority, application Great Britain, June 8, 1963, 22,933/ 63 Claims. (Cl. 34217) This invention relates to means for preparing gastreated objects of which the primary example to which it applies is the treatment by ammonia gas for hardening, and the air-drying, of ceramic shell moulds such as are used in the investment casting process. The means of the invention may, however, be applicable to analogous methods or processes wherein objects are required to be treated by a gas and then exposed to currents of air for drying. Further steps may also be facilitated by the apparatus, as will become apparent.

In relation to the primary purpose of the invention, the objects sought include the provision of an apparatus in which ammonia can be used without elaborate sealing, and its evacuation and purging together with efiicient circulation of air, are ensured. It is also a convenient apparatus for series production either of single objects or batches (depending on their size) of objects. Thus it may be use-d for example in the production of ceramic moulded objects such as hollow-ware, crockery, or the like. Further an object is to achieve relatively rapid treatment which is not only advantageous in itself but tends to avoid cracking of the objects particularly if (as in the case of wax patterns) a pattern or form is left within the object. The apparatus is of relatively low cost. Small quantities can be processed quickly, because time may be saved between applications of coats; this applies especially in such a case as shell-moulding in which the mould is made by applying repeated coats to the pattern.

Generally according to the invention, apparatus for the purpose of gas-treating of objects comprises a plurality of chambers (collectively to be described as a rotor) symmetrically disposed around a preferably vertical axis and rotatable about this axis, in relation to fixed structure, means to enable the rotor to be so rotated between stations intermittently through an angle corresponding to that which is subtended by a chamber (or to be rotated slowly), provision at at least one station for supply to each chamber in sequence of the treatment gas used (e.g. ammonia) and means for ventilating the chambers in their further rotation with a flow of air, whilst at at least one station (preferably that which in the cycle precedes the gassing station) access is provided for unloading and loading objects into the chambers, or the whole rotor may be removable for this purpose.

Further according to the invention, the rotor is preferably arranged as a series of radial walls collectively rotatable about a vertical axis within a fixed structure comprising a cylindrical casing, and having a coaxial tube extending through it to suck a flow of air through the chamber from a common chamber at the bottom; valve means at one station operated by the rotation of the rotor to admit a controlled volume of gas to the chamber which is at that station; an escape passage from each chamber which is in the ventilation phase into the tube and access means to each chamber for its loading and unloading; this may simply be an opening through the rotor into each chamber to register with an opening in the casing at the loading station. For loading and unloading the rotor may be removable as a whole (to be replaced if required by a reloaded one).

The rotor preferably has a perforated floor, and is supported on a ball bearing surrounding the bottom end of the central air tube, and carried by a flange. The flange "ice is extended by a floor beneath the rotor, and this floof forming a false floor of the casing, may have openings corresponding to the perforations of the floor of the rotor but not at the gassing station. Mounted on the rotor there are cams corresponding to each chamber, and these in sequence strike a cam-follower which opens a valve or operates a metering discharge device, whereby a predetermined charge of ammonia gas is injected into each chamber as it is stopped at or slowly passes this station. A further valve arrangement, or the simple obstruction of a port, cuts off the chamber at this station from the air supply which otherwise would pass through it into the coaxial tube. Thus, at the gassing station a known volume of ammonia is charged into each chamber, and the other chambers are continually being purged by air flow, and of course dried.

At the station following the gassing station, the gases from the chamber at that station may be separately vented, since at this phase the concentration of ammonia or other noxious gas is or may be too high to permit its ventilization by the same means as that of later phases.

Purging may depend entirely on suction, or there may be a supply of compressed air into the device, or both.

The drawing illustrates one example of the invention as specifically realised for the treatment of ceramic shell moulds by ammonia gas and their purging and drying.

FIGURE 1 is a sectional elevation (on A-A of FIG- URE 2).

FIGURE 2 is a plan view partly cut away.

A rotor consists of six vertical walls 1, attached at their bottom edges to a circular floor 2 and at their top edges to a circular top 3 which is of substantially greater diameter. The inner vertical edges of wall 1 are attached to a central vertical tube 4, and at the bottom, surrounding the tube 4 and attached to the floor 2, is a robust annular bearing ring 6 having a circular groove to form a ballrace for bearing balls 7. The peripheral edges of the walls 1 are bent flange-wise for stifiness, as shown at 1A.

Fixed structure, forming a casing, consists of a cylindrical wall 8 which has a fairly close clearance from the edges at 1A. The top 3 has a downward annular flange 3A outside the upper margin of wall 8. The wall 8 is attached to a'base structure or under-floor 9, below a false floor 10 which is circular, and from the centre of which extends upwardly a fixed tube 11 within the tube 4 and extending from the upper end thereof to any suitable suction ventilation system, for flow in the sense of the arrow 11A. The floor 10 is marginally attached to the wall 8, and centrally carries a second bearing-ring 6A complementary to 6 and supporting the weight of the rotor, as through a structural member 9A. The bearing is provided for lubrication by an externally accessible pipe 7A.

The rotor as a whole has, attached to its top 3, conveniently disposed handles 12. At a chosen point, there may be a locking or detent device to locate the rotor at its stations, i.e. at each 60 of its rotation.

At one station, called the loading station, the Wall 8 of the casing is cut away as at 8A to give access to the chambers defined by the walls 1 of the rotor. These chambers may have shelves, racks, or other provision of supporting several articles to be treated, and such may be slidably removable as a whole to be replaced by a newlyloaded batch.

The floor 2, in each chamber, is perforated or ported as indicated by a hole at 2A. The floor 10 is likewise perforated (10A) in registry with the holes 2A, except in the gassing station. The gassing station is that which (in the sequence of rotation) follows the loading station. Thus the rotor being moved as shown by the arrow 13 within the casing, each chamber .now loaded, comes to the gassing station which is characterised by having a gas inlet at 14 in the wall 8. Having no registering port exposed in that station for its free escape, ammonia is supplied to each chamber in turn. This is preferably effected automatically by one of six cam members 15 attached to the rotor and positioned so as to strike and move a cam-follower 26 controlling a valve 25 to release .a predetermined charge of ammonia into the gassing chamber, through 14.

The top 3 is perforated with holes as indicated at 3B. The tube 11 supports, above the rotor, and by stiffening struts 16, an annular plate 16A of lesser diameter than the circle of holes at 3B, but this carries a segmental extension plate 16B extending over the loading station and gassing station, so as to cover and obstruct air entry into the holes 3B when located at these stations. Thus the plate 16B acts in effect as a throttle or valve, to prevent free ingress of air at these stations to the chambers. Alternatively, air inlet holes may be provided at the purging stations, in the wall 8.

Operation is thus. The object being loaded into a chamber of the rotor, the operator (unlocking if necessary) rotates the rotor through 60. This brings the object into the gassing station and the corresponding cam 15 causes that chamber to be charged with ammonia. The next movement of the rotor brings that object to the first purging station (shown generally at 17) where the suction then effected through tube 11, holes 2A and holes 3B, causes a current of air to flow through the chamber and purges it, also contributing to drying of the object. This operation is pursued through the next two chambers. The presence of the plate 16B prevents unnecessary and undesirable flow of air through the gassing station.

Whilst for convenience only one set of holes is illustrated for each chamber, evidently a plurality of such holes or other perforations may be provided.

It is also clear that considerable modification in other details is within the invention For example the whole rotor may be steadily but slowly rotated and be powerdriven for that purpose. The rotor as a whole may be arranged to be removable (subject to alteration of the parts 16A, 16B) so that a loaded rotor may be removed and replaced by another. Station-locking means is not essential providing the operator can easily index the rotor around by stations. There can be a supply of compressed air as well as or instead of a suction system. A separate suction-collector may be provided for the first purging station so that a strong concentration of the treatment gas is exhausted separately from the subsequent purgings.

In a plant of large size, the stations for loading, gassing and purging may occupy say half, or some other proper fraction, of the total revolution of the rotor.

For the better distribution of gas and air, baffles or other provision may be made Within the rotor. In the event that considerable condensation may arise, drainage, as by sloping floor surfaces towards holes may be afforded.

The rotor may easily be hand-rotated, there being a gravity lock to register each chamber in turn. It may, however, be power-rotated and a time-switch may be used to control its station-by-station rotation; or where the time of the process permits, the rotor may continuously rotate, but slowly enough to permit unloading and loading.

The final outlet of air and gas is preferably connected to a discharge duct dispensing it at some harmless location, this being achieved either by using an extractor fan or blower.

I claim:

1. Apparatus for gas testing objects, said apparatus comprising: means forming a rotor symmetrically disposed about and rotatable about a vertical axis, said rotor being divided into a plurality of chambers by a series of radially extending vertical walls, a stationary cylindrical casing substantially surrounding said rotor and in which said rotor is rotatable, said stationary cylindrical casing having a vertical coaxial tube extending therethrough coaxially with the axis of said rotor and adapted for connection at its upper end to a suction source, means forming a common chamber at the bottom of said stationary cylindrical casing below said rotor, said tube communicating at its lower end with said common chamber, means enabling said rotor to be rotated successively through angles subtending a chamber of the rotor so as to have each rotor pass through successive stations around the stationary cylindrical casing, valve means at one station operated by the rotation of said rotor for supplying a volume of treatment gas to each chamber while the chamber is at that station, means permitting loading and unloading of objects into and from the chambers at a loading and unloading station prior in rotational sequence to the station at which treatment gas is supplied to the chambers, and means for ventilating the chambers between the treatment gas supplying station and the loading and unloading station by selectively opening the chambers to a supply of purging gas and to said common chamber whereby the purging gas will be drawn through the rotor chambers into said common chamber and up said coaxial tube.

2. Apparatus as set forth in claim 1 wherein said means permitting loading and unloading comprises access means in the wall of said stationary cylindrical casing.

3. Apparatus as claimed in claim 2 wherein said rotor is provided with a perforated floor.

4. Apparatus as claimed in claim 3 wherein said rotor is supported on a ball bearing surrounding the bottom end of the coaxial tube and carried by a flange.

5. Apparatus as set forth in claim 4 wherein the flange is extended by a floor beneath the rotor which forms a false floor of the casing, openings corresponding to the perforations of the rotor floor are provided in the false floor at each station except the treatment gas supplying station to open said rotor chambers to said common chamber to effect said ventilating.

6. Apparatus as claimed in claim 5 wherein said chamber is provided with an opening through which the flow of purging gas enters the chamber.

7. Apparatus as set forth in claim 6 wherein said openings communicate with ambient atmosphere, said purging gas being air.

8. Apparatus as set forth in claim 7 wherein means are provided for closing said openings when the corresponding chamber is at the treatment gas supplying station.

9. Apparatus as set forth in claim 8 wherein said means for closing said openings comprises a segmental plate, subtended from the coaxial tube over the top of the rotor at the treatment gas supplying station to obstruct and close said openings, which are provided in the roof of each chamber.

10. Apparatus as set forth in claim 1 wherein said valve means is actuated by a cam follower, the cam follower being struck in sequence by cams mounted on the rotor and corresponding to each other.

References Cited by the Examiner UNITED STATES PATENTS 1,903,909 5/1933 Cope et al. 148-166 X 2,256,017 9/1941 Curran 3437 X 3,063,878 11/1962 Wilson 14813 FREDERICK L. MATTESON, JR., Primary Examiner. JOHN J. CAMBY, Examiner. 

1. APPARATUS FOR GAS TESTING OBJECTS, SAID APPARATUS COMPRISING: MEANS FORMING A ROTOR SYMMETRICALLY DISPOSED ABOUT AND ROTATABLE ABOUT A VERTICAL AXIS, SAID ROTOR BEING DIVIDED INTO A PLURALITY OF CHAMBERS BY A SERIES OF RADIALLY EXTENDING VERTICAL WALLS, A STATIONARY CYLINDRICAL CASING SUBSTANTIALLY SURROUNDING SAID ROTOR AND IN WHICH SAID ROTOR IS ROTATABLE, SAID STATIONARY CYLINDRICAL CASING HAVING A VERTICAL COAXIAL TUBE EXTENDING THERETHROUGH COAXIALLY WITH THE AXIS OF SAID ROTOR AND ADAPTED FOR CONNECTION AT ITS UPPER END TO A SUCTION SOURCE, MEANS FORMING A COMMON CHAMBER AT THE BOTTOM OF SAID STATIONARY CYLINDRICAL CASING BELOW SAID ROTOR, SAID TUBE COMMUNICATING AT ITS LOWER END WITH SAID COMMON CHAMBER, MEANS ENABLING SAID ROTOR TO BE ROTATED SUCCESSIVELY THROUGH ANGLES SUBTENDING A CHAMBER OF THE ROTOR SO AS TO HAVE EACH ROTOR PASS THROUGH SUCCESSIVE STATIONS AROUND 